First Results on the Experimental Search for $\eta ^\prime $-Mesic Nuclei with the $^{12}$C($p,d$) Reaction

We performed a missing-mass spectroscopy experiment of the C-12(p, d) reaction in order to search for eta'-mesic nuclei. Excitation spectrum of C-11 around the eta'-meson production threshold was successfully obtained with a high-statistical sensitivity and sufficiently good energy resolution. Since no peak structure associated with the formation of eta'-mesic nuclei was observed, we set constraints on the formation cross sections of eta'-mesic states and on the eta'-nucleus interaction.